Jabiru, no spark

[Kevin]

Hi folks, just joined to help a friend with a new Jabiru that doesn't have spark from either coil on one of six cylinders.

 

All other cylinders are fine.

 

Any ideas on what could be causing this?

 

Thanks.

 

 

[Peter008]

Sounds like the plug wires are on the wrong terminals of the distributor cap. It is easy to get wrong but would have to be wrong on both caps for no spark to be at either plug.

 

There will be a diagram in the Jab manual.

 

 

[Kevin]

If the wires were on the wrong terminals would there not still be a spark generated through the coils?

 

The firing sequence would be incorrect but I am guessing a spark would be present at one or both plugs.

 

 

[Peter008]

I had made the assumption that the 'no spark' was describing a miss in the running of the engine. The coil would still energise the plug but no where near the compression stroke and therefore develop a miss.

 

 

[Kevin]

When he started the engine for the first time it was running rough but that was due to the one cylinder not firing.

 

The problem seems to be before the distributors because we switched wires on the distributors and there is no spark present.

 

The magnets appear fine, gap is good on the coils, wires test ok .

 

Just an odd trouble when we have two coils and two distributors with no spark on the same position.

 

 

[JEM]

Have you tried the Jabiru Tech Forums run by Jabiru themselves?

 

Topics in Jabiru Aircraft (1/1) - Jabiru Aircraft - Jabiru Aircraft & Engines Australia

 

 

[Kevin]

Yes, I wrote to them yesterday and I am awaiting their response.

 

I don't know if this could be timing related, it's fixed and not adjustable.

 

The engine was said to be tested at the factory so I can only assume they would have caught the problem there prior to shipping it.

 

 

[Peter008]

Please keep us advised on what is found. It sounds like an interesting problem.

 

 

[planesmaker]

how did you test for no spark? removing sparkplugs and resting plugs on motor? is it possible it is simply 2 damaged plugs? rare but cant see it can be anything else if all others are working. another thing is to start it in the dark with top cowl removed to see if you are leaking spark somewhere from a lead. actually i remember we had a similar problem it waswhere the leads plug into the cap one lead was just touching carby, turned it in the distributor socket and fixed. spark was leaking from joint in lead and endcap. worth looking at. it was on an engine just come from owner rebuild at jabiru.

 

 

[Kevin]

It really is an odd problem considering the redundancy.

 

The spark was tested using an inline test light between the wire and the plug.

 

Not getting a spark on #6 only from the same rotor position on both distributors.

 

I read someone had the same problem with #1 and he got it going after replacing both coils.

 

two brand new Camit coils

Here's a link to the conversation

Jabiru Owners Group • View topic - Rotor Arms

 

 

[planesmaker]

if the coils are working for othercylinders then they should work for #6.Spark for #6 is leaking to earth somewhere between dist cap and plug on both ignitions.

 

 

[planesmaker]

you said you switched wires on the distributors, what wires did you switch?

 

 

[Kevin]

planesmaker; Switched with other wires from another cylinder to eliminate a cable problem.

 

Tested the leads from the distributor still attached to the plugs for ground and they test clean.

 

 

[planesmaker]

you going to have us all going mad

 

 

[Kevin]

What is it they say? Misery loves company!

 

You did put a thought in my head and I called him to put the rotor over the firing position for #6 and then test the cable attached to the plug.

 

When I tested the cables they were likely off that position.

 

 

[Kevin]

Update, looks like a weak spark on #6 instead of no spark.

 

Changed test light and can now see a faint spark on #6.

 

 

[pmccarthy]

I had the recent experience on a car that the test light will not light with a dud plug. I thought the test light would show me whether sufficient volts/amps/power was reaching the plug, but it didn't light up because the plug was carboned up. So a mixture/oil/temp problem could foul both plugs and the light would not light up.

 

 

[crashley]

Have you checked the distributor cap for a proper fit ie is the rotor running true there may be a bigger gap when at number 6 plug It is strange that it is only on the number 6 plugs as the only thing that is not common to all plugs is the terms in the cap and the plug wire which I think you have checked

 

 

[facthunter]

Have you checked the distributor position is such as to align the rotor with the terminal at the point of the spark happening? It can actually be OFF the terminal or nearly so. I have had people tell me you can time the engine by moving the distributor. That would not show much understanding of the system. Magneto's should have brushes contacting, rather than gaps with sparks jumping them. Nev

 

 

[Yenn]

This thread started with no spark at either plug on the same cylinde. That means that the other plugs are all getting power. Crossed leads would not give this problem.Now we hear that there is a faint spark.

 

Is this problem a case of no spark or is it a case of one cylinder not firing?

 

The cylinder could fail to fire because of both plugs fouling.

 

New plugs would show if that is the case. If there is only a faint spark from each coil, than something is affecting the system, between both coils and the plugs. It would be coincidence if the same problem happened to each system, unless there was some way that there was mechanical damage to both systems.tell us again exactly what the problem is and what you have done, it intrigues me.

 

 

[Jaba-who]

I'm with Yenn. It sounds like you have to exclude problems in the common parts of the system and the only things that are common are the cylinder. So you gotta start at the cylinder.

 

The two plugs could be functionally OK but can be directly affected by the gas in the cylinder - fouling etc.

 

so clean or change the plugs.

 

The plugs could both be defective - good chance they are from the same batch if they were installed at same time from a stock supply.

 

So change the plugs.

 

Hard to believe you would get similar failures on similar parts of two independent systems beyond that. ( and they seem to have been excluded anyway)